This project is concerned with identification and characterization of component of the lung associated with pulmonary diseases which could provide information concerning the disease processes as well as function as diagnostic markers of pulmonary damage or disease. Current attention has been focused on the multi-lamellated myelin-like structures which accumulate in the alveoli and airways of patients with pulmonary alveolar proteinosis. The objectives of the study have been to elucidate the composition, structure and origins of this unusual material.